Quack

So I was in English Class today thinking about Nerf mods as usual when I came across an interesting solution I have been having with two stage flywheel builds. In a typical single stage build the motors are wired in parallel so that the entire voltage of the battery drops across each motor causing them to spin at their max rpm for the given voltage of the battery. However this means that the maximum current drawn by the motors in this setup is the sum of their stall currents. In a single stage setup this will top out at ~50A for the thirstiest motors and shouldn't be that much of a problem for a typical 3s battery. However in a two stage or more build with 4+ motors being used, this current draw could be over 100A! Not only is this much more than many 3s batteries are rated for, but it is incredibly dangerous. However, by rethinking the motor wiring, I think this issue can be solved. By wiring each set of motors in series and them those sets in parallel, the amount of current drawn is halved. On the flip side, double of the amount of voltage is required to spin the motors to the same RPM. I have been doing some searching and found this 6s battery which I think should be able to accomplish the job and isn't too much more expensive than a 3s. I have some diagrams below showing the difference in wiring. I'd like to know what you guys think since I'm only 85% positive on my physics. 

 paralell 2 stage.png   358.03KB   115 downloads

 series 2 stage.png   213.07KB   115 downloads

After taking the advice of the community in my previous topic (link for those who want to see), I ordered a pair of brushless motors the equivalent in speed to a stock Nerf blaster. Here are my findings. 

 

1. Brushless motors are expensive

I probably bought some of the cheapest motors I could probably buy, however, if I was going to do this again, I would probably buy ones that are a little bit more powerful. The problem with brushless motors is that you cant just buy the motors and be done with it. You also need ESC's and a servo tester to run your setup. While My ESC's were already coded, you may even want to buy a programming card so you can add this like electronic braking if you want (more on that later).

2. Lipos or other rc batteries are a necessity

Brushless motors are meant to work off of Lipo batteries. The product description should tell you which one. That means, in order to use brushless motors, you must have a lipo battery and a charger at least (battery alarm recommended). You can use other battery chemistries, but you might have to figure out the power equivalent yourself.

3. ESC's are a cool Idea for nerf

Because ESC's are programmable you can have your motors do all sorts of things. Perhaps most useful to nerf is electronic braking. Forget complicated circuitry, with an ESC you have the ability to have electronic braking built right in.

4. Inrunner vs. Outrunner motors

There are two main types of brushless motors, Inrunner and Outrunner. Inrunner motors act similarly to regular brushed motors in that only the shaft spins. However these tend to overheat easier and need to have flywheels attached to work in Nerf blasters. Outrunner motors on the other hand act a little different to regular brushed motors. Instead, the outer bell of the motor turns while the inside stays stationary (the bottom of the motor mounts to whatever the motor is being placed on). These motors are great because they act as their own flywheels. On top of that, they have more torque because the outside is spinning and they run cooler. The motors I bought were outrunners.

5. Wiring

Brushless motors require a lot of wiring. None of the wiring is that difficult, however there are a couple things you have to keep in mind. First, you may have to wire battery connectors. My ESC's came with leads to connect to my battery, but I had to wire the connectors themselves. On top of that, I had to wire the harness to split the battery so that both motors ran off the one battery, it was a lot more solodering and shrink wrap than your basic stryfe mod.

6. Sound

My brushless motors are very quiet. I don't know how much sound level increases as the power does, But my motors only change in pitch when they are "revved" up.

 

Overall I think brushless motors are for those who really want to go all out in a flywheel mod. They are especially helpful for rivals rounds so that is where they might shine, but they only other reason you would need such torque was if your flywheels were metal (assuming you're going to use an inrunner motor). While Brushless motors may have the option of electronic braking, they will also require massive shell modification. Perhaps they are most useful in flywheel homemades like the one I am building. I don't really want to put down how to wire them up, but if enough people are interested, I guess I could try my best.

 

Here is my setup.

After finally getting my hands on a 3d printer I've decided to take on a very ambitious project. I am attempting to 3d print a flywheel rivals blaster. However I have hit a problem when working on my first prototype. How it works is you hold onto the handle and press the button with your thumb, and then you feed balls into it with the other hand. The moters, which are just some old rapidstrike motors I am using until I get some shark nsr 40's, are powered by three trustfires and a dummy battery. Everything worked well until I started testing. pushing the HIR's in I would only get about a 5 foot range, I adjusted to flywheels so that they would only compress the HIR's 0.5mm instead of 2mm, but I only ended up with about a 10 foot range increase. What I've been thinking is that my stock motors don't have enough torque (something that would be fixed by dropping in sharks), but while I'm at it, I've also been wondering how flywheel weight comes into the equation. My flywheels are standard weight but is there any advantage to making them lighter or heavier? Hopefully some modding experience and maybe a little physics can help.

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Prototype

Side view

Battery pack

Flywheel bottom

Flywheel top

Flywheel side

Every hobby seems to have a series of magazines that are enjoyable to read and a helpful source of information. What I think would be kind of cool is if we had a magazine for the NIC. I made a sample issue on this site called lucid press which allows you to create digital magazines brochures etc. I am currently on a free trial but I thought that if the magazine would actually be created then the sponsers could split up the price based on what precentage of the ads they have. I would need a graphic designer (trust me I need help on that) for the covers and other design related things, 3 to 5 writers, and a proofreader/editor. I will contribute some articles but writing a full magazine is hard work. There is a poll for features that you would like to see every month. Any suggestions should be posted below. If you are interested in contributing, please pm me.

I'm doing my second rapidstrike overhaul and since I'm using Shark nsr 40's, I wanted to do electronic braking. Does anyone have a wiring diagram of what they do or something equally helpful?